On 08/19/05 15:38, Patrick Mansfield wrote:
> On Fri, Aug 19, 2005 at 02:46:35PM -0400, Luben Tuikov wrote:
>
>
>>Using the command time out hook and the strategy routine, gives _complete_
>>control over host recovery, and I really do mean _complete_.
>>
>
>
> I assume you mean hostt->eh_timed_out.
Hi Patrick, how are you?
Yes, this is what I meant, sorry for not being clear.
> Is anyone implmenting (or has implemented) a ->eh_timed_out function? I see
> none in mainline kernel.
Yes, I have.
> I was looking at using it in an LLDD, but hit two problems, and have
> started to work on an alternate approach of cancelling (aborting or wtf you
> want to call it) a list of commands in the eh thread.
The eh_timed_out + eh_strategy_handler is actually pretty perfect,
and _complete_, for any application and purpose in recovering a
LU/device/host (in that order ;-) ).
> The two problems I see with the hook are:
>
> It calls the driver in interrupt context, so the called function can't
> sleep.
Consider this: When SCSI Core told you that the command timed out,
A) it has already finished,
B) it hasn't already finished.
In case A, you can return EH_HANDLED. In case B, you return
EH_NOT_HANDLED, and deal with it in the eh_strategy_handler.
(Hint: you can still "finish" it from there.)
EH_RESET_TIMER is not really needed provided that
- your interface infrastructure is in place,
- you set the timeout value properly in slave_configure.
> There is no queueing or list mechanism, so LLDD's that can only cancel one
> command at a time will have problem.
See above.
Luben
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